Facebook cofounder Mark Zuckerberg defended his company from accusations that the social network spread misinformation during the presidential election, but acknowledged they must work harder to “flag hoaxes and fake news” saying, “There is more we can do.”

In a post on his Facebook page on Saturday, Zuckerberg wrote:

“We don’t want any hoaxes on Facebook. Our goal is to show people the content they will find most meaningful, and people want accurate news. We have already launched work enabling our community to flag hoaxes and fake news, and there is more we can do here.”

Facebook has come under intense scrutiny for what critics call its role in spreading misinformation and hoaxes about the presidential election, much of which was aimed at Hillary Clinton and presumed to have helped Donald Trump. Others have pointed out that the filtering algorithms on Facebook tend to feed users only the type of news they want to hear, contributing to an echo-chamber effect that stifles opposing points of view or facts, a troubling trend in a democracy.

Zuckerberg initially ducked the matter this week by calling it a “pretty crazy concept” that Facebook might have swayed votes in the election, but by Saturday he clearly had second thoughts about that notion.

In his post he acknowledged the widespread criticism, noting: “After the election, many people are asking whether fake news contributed to the result, and what our responsibility is to prevent fake news from spreading. These are very important questions and I care deeply about getting them right.”

However, he insisted that 99 percent of the content on Facebook is authentic, and called it “extremely unlikely hoaxes changed the outcome of this election in one direction or the other.”

Misinformation spread on Facebook included the notion that the Pope had endorsed Donald Trump. The social network had 1.79 billion monthly active users as of the third quarter of 2016.

The defense is masking a vigorous internal debate at Facebook. A New York Times article posted on Saturday said top Facebook executives were debating internally whether the social network had a deeper responsibility in monitoring the veracity of news in the mass communication tool that its news feed has become.

An “online conversation among Facebook’s executives on Tuesday, which was one of several private message threads that began among the company’s top ranks, showed that the social network was internally questioning what its responsibilities might be,” wrote the Times.

But the task of determining what information is accurate and what isn’t is clearly complicated, and Facebook has insisted throughout its existence that it does not want to be the arbiter of information, merely a platform to connect users.

But clearly that role needs to be redefined as the platform has become a powerful tool of mass communication, which Zuckerberg acknowledged:

I” am confident we can find ways for our community to tell us what content is most meaningful, but I believe we must be extremely cautious about becoming arbiters of truth ourselves,” he said.

Our goal is to give every person a voice. We believe deeply in people. Assuming that people understand what is important in their lives and that they can express those views has driven not only our community, but democracy overall. Sometimes when people use their voice though, they say things that seem wrong and they support people you disagree with.

After the election, many people are asking whether fake news contributed to the result, and what our responsibility is to prevent fake news from spreading. These are very important questions and I care deeply about getting them right. I want to do my best to explain what we know here.

Of all the content on Facebook, more than 99% of what people see is authentic. Only a very small amount is fake news and hoaxes. The hoaxes that do exist are not limited to one partisan view, or even to politics. Overall, this makes it extremely unlikely hoaxes changed the outcome of this election in one direction or the other.

That said, we don’t want any hoaxes on Facebook. Our goal is to show people the content they will find most meaningful, and people want accurate news. We have already launched work enabling our community to flag hoaxes and fake news, and there is more we can do here. We have made progress, and we will continue to work on this to improve further.

This is an area where I believe we must proceed very carefully though. Identifying the “truth” is complicated. While some hoaxes can be completely debunked, a greater amount of content, including from mainstream sources, often gets the basic idea right but some details wrong or omitted. An even greater volume of stories express an opinion that many will disagree with and flag as incorrect even when factual. I am confident we can find ways for our community to tell us what content is most meaningful, but I believe we must be extremely cautious about becoming arbiters of truth ourselves.

As we continue our research, we are committed to always updating you on how News Feed evolves. We hope to have more to share soon, although this work often takes longer than we’d like in order to confirm changes we make won’t introduce unintended side effects or bias into the system. If you’re interested in following our updates, I encourage you to follow our News Feed FYI here: http://bit.ly/2frNWo2.

Overall, I am proud of our role giving people a voice in this election. We helped more than 2 million people register to vote, and based on our estimates we got a similar number of people to vote who might have stayed home otherwise. We helped millions of people connect with candidates so they could hear from them directly and be better informed. Most importantly, we gave tens of millions of people tools to share billions of posts and reactions about this election. A lot of that dialog may not have happened without Facebook.

This has been a historic election and it has been very painful for many people. Still, I think it’s important to try to understand the perspective of people on the other side. In my experience, people are good, and even if you may not feel that way today, believing in people leads to better results over the long term.